Flow cytometry is a technique which allows the rapid determination of cellular characteristics, usually through the utilization of fluorescent markers, and the physical separation of the cells based on those parameters. The Flow Cytometry Shared Resources of the YCC utilizes a Becton-Dickinson FACS Vantage three laser, eight parameter flow cytometer with high speed sorting capability operated by a full time director. The Shared Resource is available to all investigators, including those outside the YCC. The Resource has four major goals: to provide flow cytometry services which are of high quality, readily available and at reasonable cost, to provide technical and professional consultation to investigators in projects where flow cytometry has proven or potential use, to collaborate with investigators in research in which this technique plays a significant role, and to educate the Medical School community on the applications of flow cytometry in cancer research. The major services provided include the following: immunophenotyping, separation of cells from a mixture based on relative fluorescence, cell size, and granularity, DNA cell cycle and ploidy analysis, cellular kinetics and enzyme reporter assays. Last year the Resource was utilized by 61 investigators from 17 departments at Yale University.